639204913681 has 8 divisors (see below), whose sum is σ = 647338129920. Its totient is φ = 631072747968.

The previous prime is 639204913673. The next prime is 639204913703. The reversal of 639204913681 is 186319402936.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 639204913681 - 2³ = 639204913673 is a prime.

It is a super-2 number, since 2×639204913681² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639204913631) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1000425 + ... + 1509721.

It is an arithmetic number, because the mean of its divisors is an integer number (80917266240).

Almost surely, 2^639204913681 is an apocalyptic number.

It is an amenable number.

639204913681 is a deficient number, since it is larger than the sum of its proper divisors (8133216239).

639204913681 is a wasteful number, since it uses less digits than its factorization.

639204913681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 525263.

The product of its (nonzero) digits is 1679616, while the sum is 52.

The spelling of 639204913681 in words is "six hundred thirty-nine billion, two hundred four million, nine hundred thirteen thousand, six hundred eighty-one".